Vibrating meters, such as Coriolis mass flow meters exist, which can measure a mass flow rate of a fluid directly. While Coriolis mass flow meters have received great success in a variety of industries, there are certain situations where Coriolis mass flow meters are undesirable. For example, in some situations, the cost of using high purity metals, such as tantalum or titanium, for the flow tubes becomes prohibitively expensive in high flow situations where the size of the tubes requires an excessive amount of the metal. Another situation may be where a customer already has either a density meter or a volumetric flow meter installed in their system and simply requires the other meter in order to generate a mass flow rate. In such situations, the customer may not wish to replace the existing sensor, but rather simply add the missing measurement device in order to calculate a mass flow rate using equation (1):{dot over (m)}=Q*ρ  (1)
Where:
{dot over (m)} is the mass flow rate;
Q is the volumetric flow rate; and
ρ is the density.
One problem with the combination of a density meter and a volumetric flow meter as opposed to a Coriolis mass flow meter in order to generate a mass flow rate is the excessive amount of wiring involved as shown in FIG. 1.
FIG. 1 shows a prior art mass flow sensor system 10. The prior art mass flow sensor system 10 can include a density meter 11 and a volumetric flow meter 12. The density meter 11 and the volumetric flow meter 12 are positioned within a flow conduit 5 carrying a process fluid. The density meter 11 may comprise any one of well-known density meters, such as a Coriolis density meter, a hygrometer, an x-ray densitometer, a gamma densitometer, etc. The volumetric flow meter 12 may comprise any well-known meter that measures a volumetric flow rate, such as an ultra-sonic meter, a magnetic meter, a turbine meter, a vortex meter, etc.
The prior art mass flow sensor system 10 also includes a central processing system 13. As shown, the density meter 11 is in electrical communication with the central processing system 13 via electrical leads 14. Similarly, the volumetric flow meter 12 is in electrical communication with the central processing system 13 via electrical leads 15. Therefore, each of the meters 11, 12 sends signals to the central processing system 13. The central processing system 13 processes the signals received from the density meter 11 to generate a density measurement. Likewise, the central processing system 13 processes the signals received from the volumetric flow meter 12 to generate a volumetric flow rate. The central processing system 13 may subsequently generate a mass flow rate based on the generated density and volumetric flow rate. The mass flow rate may then be provided to a user or another processing system via leads 16. As an alternative, the central processing system 13 may simply output the individual density and the volumetric flow rate without calculating a mass flow rate. The customer must then use another processing system to determine the mass flow rate based on the output from the central processing system 13.
The prior art mass flow system 10 suffers from a number of problems. One problem is due to the increased amount of wiring required. While the density meter 11 and the volumetric flow meter 12 are often located relatively close to one another, the central processing system 13 may be located remotely from the density meter 11 and the volumetric flow meter 12. Consequently, because each meter 11 and 12 communicates with the central processing system 13 independently, the amount of wiring is duplicative.
Another problem with the prior art system 10 is that if either the density meter 11 or the volumetric flow meter 12 needs to be replaced, the central processing system 13 needs to be reprogrammed to receive the new signals from the new meter. Often, the central processing system 13 may be a customer's own equipment and thus, the customer is required to perform the updated programming.
Similarly, many users simply want the mass flow rate and do not necessarily need to know the particular density or the volumetric flow rate. However, in the prior art system 10, the user is only provided signals indicating the density and the volumetric flow rate and is required to perform the calculation of the mass flow rate independently.
Therefore, there is a need in the art for a system that can provide a mass flow rate output using a density meter and a volumetric flow rate meter. Further, there is a need in the art for a system that can reduce the required wiring, especially between the meters and a central processing system. The embodiments described below overcome these and other problems and an advance in the art is achieved. The embodiments described below provide a mass flow rate system that uses one or both of the density meter and the volumetric flow rate meter to perform the mass flow calculation. Consequently, only one of the meters needs to be in communication with a central processing system. Therefore, the system outputs a mass flow rate and the wiring required to communicate with the central processing system is reduced.